As a disease developed as a result of abnormality in adrenal cortex, primary aldosteronism (PA) has been known. Primary aldosteronism is a disease in which CYP11B2 is overexpressed by adrenal adenoma or adrenal hyperplasia (Non Patent Literature 1), and autonomous production of aldosterone from adrenal gland is promoted, thereby causing hypertension or hypokalemia. In the case of unilateral adrenal lesion, it can be treated by surgical excision. However, in the case of bilateral adrenal lesion, a treatment with drug therapy is adopted.
As a drug therapy performed on primary aldosteronism, an aldosterone receptor antagonist is mainly used at present. As another target molecule in drug therapy, an aldosterone synthase, CYP11B2, has been considered (Non Patent Literature 2).
Etomidate has been used as an intravenous anesthetic in another country than Japan, and has been known to mainly bind to cortisol, corticosterone, and 11β hydroxylase (CYP11B1) necessary for biosynthesis of aldosterone and inhibits them, thereby suppressing steroid synthesis in adrenal cortex (Non Patent Literature 3). Thus, it has been reported that etomidate has such side effects that it causes reductions in concentrations of aldosterone and cortisol in plasma (Non Patent Literature 4).
In addition, in recent years, aiming for non-invasive local diagnosis of aldosterone-producing adenoma and other adrenal lesions, an attempt of imaging adrenal lesions by single-photon emission computed tomography (SPECT) or positron emission tomography (PET) has been made in humans. Patent Literatures 1 and 2 and Non Patent Literatures 5 to 8 have reported various types of radiolabeled compounds targeting adrenal steroid biosynthetic enzymes. For example, results of clinical studies are disclosed on 11C-labeled metomidate in Non Patent Literatures 5 and 8, on 18F-labeled etomidate in Non Patent Literature 6, and on 123I-labeled iodometomidate in Non Patent Literatures 7 and 9. It has been reported that adrenal lesions can be imaged using these radiolabeled compounds.